1. Field of the Invention
The present invention relates to an infrared lens unit and an infrared camera system provided with the infrared lens unit.
2. Background Art
Infrared cameras have been required compensation of a photographed image because of infrared sensing errors due to variations in sensitivity of infrared detectors. Accordingly, in many of the infrared cameras, a shutter is shut to perform offset compensation, and then an offset data is obtained to update the sensitivity compensation data, as disclosed in Japanese Patent Laid-Open No. 2005-236550 “Infrared Camera”. Then, the sensitivity compensation data previously obtained is stored in a memory in the infrared camera-module and photographed image is compensated according to the data.
However, the infrared camera disclosed in Japanese Patent Laid-Open No. 2005-236550 cannot achieve a sufficient compensation effect in image focusing in an environment where the heat radiated from the lens barrel or the optical system is different from the heat radiated at the time when the sensitivity compensation data is obtained even when image compensation is performed according to the sensitivity compensation data previously obtained. Incidentally, such environmental changes described above are caused by changes in sensitivity of infrared detectors by aging or factors such as stray light that occurs in the lens barrel. That is, on an infrared camera, such environmental changes may occur even a sensitivity compensation data is updated. As described above, it has been investigated how to make the environments when sensitivity compensation data is obtained and image focusing identical to each other to obtain an image excellent in definition.
The present invention has been investigated in view of the conventional problem and an object of the present invention is to provide an infrared camera system which can obtain an image excellent in definition without being affected by an environment in which the camera is used.